The invention relates to an inductive device comprising a ferromagnetic core which contains two U-shaped parts whose limbs are directed towards each other, which parts form a magnetic circuit interrupted by an airgap. At least one pair of limbs point towards each other and are surrounded by a coil former made from an electrically insulating material.
An example of such a device is known from GS-A-1,246,458 (PHN 2884). A description is given therein of a transformer whose ferromagnetic core between the ends of each pair of limbs directed towards each other contains an airgap which is filled with a mixture of hard granules and an adhesive. The diameter of the granules, for example glass granules, determines the width of the airgap. The adhesive with the glass granules has to be applied by hand because the presence of the granules would soon make an automatic feed device defective as a result of the clogging or leakage of valves. Furthermore, granules possessing the required accurately defined size may be difficult to obtain and are expensive.